High pressure pump

ABSTRACT

A high pressure pump including a pump body, a pump housing within which at least part of the pump body is located, a gallery defined between the pump body and the pump housing, the pump body having a pump outlet which communicates with the gallery, and the pump housing having an outlet port which communicates with the gallery, and a filler located within the gallery, the filler being located at least in the part of the gallery most remote from the pump outlet.

This invention relates to a high pressure pump, and in particular to ahigh pressure pump for use in the supply of oil to a generator.

EP1486675 describes an electrical generator for use in aerospaceapplications. In order to provide lubrication for the bearings of thegenerator, and to provide cooling for the generator, a high pressure oilpump is provided. The high pressure pump takes the form of a two stagepump including a first stage in the form of a centrifugal pump wherebyoil is drawn from a reservoir and delivered to a second stage in theform of a gerotor pump. The gerotor pump delivers oil under highpressure to a manifold of the generator from which it is supplied forthe aforementioned cooling and lubrication purposes.

In practice, the second stage may comprise two gerotor pumps arranged inseries with one another so as to raise the oil pressure still further.

The pump includes a pump body located within a pump housing. The pumpbody and/or housing are shaped so as to define, therebetween, an annulargallery with which the outlet of the second stage communicates, theannular gallery communicating with an outlet port provided in the pumphousing and from which the oil is delivered under high pressure to themanifold.

The nature of a gerotor pump is such that pressure pulses develop at theoutlet thereof. It has been found that erosion occurs in the part of theannular gallery furthest from the outlet of the second stage of thepump. This erosion can result in damage to the pump body and/or the pumphousing, and/or to seals located therebetween at this point, resultingin the escape of oil therefrom. As a result, the rate of delivery of oilby the pump, and the pressure at which the oil is delivered may reduce.Reductions in the rate of oil delivery or pressure at which the oil isdelivered may result in insufficient cooling of the generator and/or ininsufficient lubrication of the bearings thereof. Clearly, this isundesirable as damage to the generator may occur. Furthermore, as thegenerator will typically incorporate sensors to detect the oil pressureand the temperature of the generator, and a control system whichcontrols the operation of the generator using the outputs of suchsensors, the control system may cause the generator to be shut down as aresult of insufficient oil being delivered.

It is an object of the invention to provide a high pressure pump inwhich at least some of the disadvantages set out hereinbefore areovercome or are of reduce effect.

According to the present invention there is provided a high pressurepump comprising a pump body, a pump housing within which at least partof the pump body is located, a gallery defined between the pump body andthe pump housing, the pump body having a pump outlet which communicateswith the gallery, and the pump housing having an outlet port whichcommunicates with the gallery, and a filler located within the gallery,the filler being located at least in the part of the gallery most remotefrom the pump outlet.

The gallery is conveniently of annular form. The filler preferablyextends about at least half of the circumferential length of thegallery. Conveniently, it extends about at least three quarters of thegallery. The cross-sectional shape of the filler conveniently conformswith that of the gallery. Consequently, the filler substantially fillsat least the part of the gallery furthest from the pump outlet.

The filler is conveniently of an elastomeric material. For example, itmay be of moulded fluorocarbon form. The filler preferably forms aninterference fit in the gallery.

Locator means are preferably provided to resist movement of the fillerwithin the gallery. The locator means may comprises locator pinsprovided in the gallery and arranged to abut the ends of the filler toresist movement of the filler. The filler may incorporate an integralprojection adapted to be received within a corresponding recess formedin the pump body and/or pump housing to resist movement of the filler.

Adjacent the gallery, the pump body and pump housing are preferablysealed to one another, for example by the use of o-ring seals.

The high pressure pump conveniently incorporates at least one gerotorpump.

It is thought that in the known high pressure pump, the erosion and wearwhich occurs results from cavitation erosion caused by pressure spikesor ripples being transmitted from the pump outlet around the gallery inboth directions. By providing the filler, the contact with and/or thequantity of oil within the part of the gallery most remote from the pumpoutlet and so most susceptible to such cavitation erosion is reduced,and as a consequence, the occurrence of such erosion is reduced.Furthermore, by the use of an elastomeric material for the filler, itmay be possible to partially absorb the pressure spikes and so reducethe occurrence of cavitation erosion.

The invention will further be described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a sectional view illustrating a high pressure pump inaccordance with an embodiment of the invention;

FIG. 2 is a diagram illustrating part of the pump of FIG. 1;

FIG. 3 is a perspective view illustrating part of the pump of FIG. 1;

FIG. 4 is a view illustrating another part of the pump; and

FIG. 5 is a view illustrating a modification.

Referring firstly to FIGS. 1 and 2, a high pressure pump is illustrated,the pump being intended for use in the supply of oil to a generator forlubrication and cooling purposes. Whilst described in connection with apump for such use, it will be appreciated that the invention is notrestricted in this regard and may be used in other applications.

The pump comprises a pump body 10 of generally stepped cylindrical shapeand through which a drive shaft 12 extends. The drive shaft 12 carries,at one end thereof, the rotor 14 of a centrifugal pump 16, operation ofthe centrifugal pump 16 serving to draw oil from a sump (not shown)along an inlet pipe 18, delivering the oil to a sump 20 located within apump housing 22. The pump body 10 is located, at least in part, withinthe pump housing 22 and is secured thereto against movement, in use.

The pump body 10 houses a gerotor type pump 24 having a pump inlet 25communicating, in use, with the sump 20, and a pump outlet 26, thegerotor type pump 24 serving to deliver oil supplied thereto, from thesump 20, to the pump outlet 26 at high pressure.

The pump body 10 defines, on its outer periphery, and annular recess 28which, together with the pump housing 22, forms an annular gallery 30.As shown in FIG. 2, the pump outlet 26 communicates with the annulargallery 30, thus the output from the gerotor pump 24 is supplied to theannular gallery 30.

As shown in FIG. 1, the pump housing 22 includes an outlet port 32 whichcommunicates, via an outlet passage 34, with the annular gallery 30.Accordingly, operation of the gerotor pump serves to deliver oil at highpressure to the outlet port 32 from where it may be delivered via amanifold or the like, if desired, to an associated electrical generatorfor lubrication and/or cooling purposes.

The pump outlet 26 is substantially aligned with the point at which theoutlet passage 34 opens into the annular gallery 30, in use.

Adjacent the annular gallery 30, the pump body 10 is provided withannular grooves in which o-ring seals 36, 38 are provided, the o-ringseals bearing against the pump housing 22 to form seals therewith and soresist the escape of oil from the annular gallery 30 either back towardsthe sump 20 or out of the pump and into the interior of the generator inan uncontrolled manner.

A gerotor pump produces pressure ripples or spikes at its outlet, inuse. As mentioned hereinbefore, it has been found that increased levelsof wear are experienced in the part of the annular gallery 30 furthestfrom the pump outlet 26. This wear can result in damage to the pumphousing and/or body with which the seals engage and/or in damage to theo-ring seals 36, 38 at or close to this location, reducing theeffectiveness of the seals. The damage to the seals or sealing effectcan result in the escape of oil from the pump, or in the return of oilto the sump 20, reducing the rate at which oil is delivered to theoutlet port 32 and/or the pressure at which oil is delivered. This cangive rise to increased wear and/or overheating of the generator, or mayresult in the generator being switched off by its associated controlleras a result of insufficient oil pressure being detected. It is thoughtthat the increased levels of wear arising at the part of the annulargallery most remote from the pump outlet 26 are caused by cavitationerosion. It is thought that the pressure ripples or spikes aretransmitted in both directions around the annular gallery from the pumpoutlet 26, and so the pressure fluctuations experienced at the pointfurthest from the pump outlet 26 are significantly greater than thoseexperienced elsewhere. The range of pressures experienced at thislocation are approximately twice those experienced elsewhere. Cavitationerosion is thus thought to be most significant at the point most remotefrom the pump outlet 26, and this is thought to be the cause of theaccelerated wear at this location.

In accordance with this embodiment of the invention, as shown in FIGS. 1and 3, a filler element 40 is located within the annular gallery 30. Thefiller element 40 cannot extend about the entire circumference of theannular gallery 30 as this would prevent or restrict the flow of oilbetween the pump outlet 26 and the outlet passage 34. Rather, therefore,the filler element 40 extends around only part of the circumferentiallength of the gallery 30. The part of the gallery 30 in which the fillerelement 40 is located includes the part thereof furthest from the pumpoutlet 26. However, the filler element 40 is conveniently long enoughthat it extends about at least half of the circumferential length of theannular gallery 30. Preferably, it extends about considerably more ofthe annular gallery 30 than this. By way of example, in the illustratedembodiment, the filler element 40 extends around about three quarters ofthe annular gallery 30.

The dimensions of the filler element 40 are conveniently such that thefiller element 40 substantially fills the relevant parts of the annulargallery 30, leaving little if any space available to accommodate oil.Preferably the filler element 40 is an interference fit within theannular gallery 30.

It is thought that by substantially filling the relevant parts of theannular gallery 30 with the filler element 40, contact between thepressurised oil and the housing 22, and/or the transmission of pressureripples or spikes to the part of the annular gallery 30 most remote fromthe pump outlet 26, is reduced or avoided, thus the occurrence ofcavitation erosion at that location is avoided or significantly reduced.By avoiding such cavitation erosion, damage in the region of the o-ringseals 36, 38 and the parts providing support therefore is reduced and sothe output of the pump is maintained.

The filler element 40 is preferably of an elastomeric material. As aresult, not only does the filler element 40 serves to reduce the passageof oil to the part of the annular gallery 30 most remote from the pumpoutlet 26, but also compression and subsequent relaxation of theelastomeric material may serve to partially absorb the pressure spikes,further reducing the impact of cavitation erosion at the part of theannular gallery 30 most remote from the pump outlet 26. By way ofexample, the filler element 40 may be of moulded fluorocarbon form.

As the filler element 40 does not extend around the entirety of theannular gallery 30, it is important for it to be held against movementrelative to the pump housing 22 and/or pump body 10 in order to ensurethat the filler element 40 does not block the pump outlet 26 or outletpassage 34. In some circumstances, this may be achieved simply by virtueof the frictional forces experienced between the filler element 40 andthe walls defining the annular gallery 30. However, it is desirable toprovide location means serving to positively resist movement of thefiller element 40.

As shown in FIG. 3, the location means may comprise a projection or boss42 integrally formed with the filler element 40 and arranged to bereceived within a corresponding recess 44 formed in the pump housing 22,as shown in FIG. 4.

Alternatively, the boss 42 may be located and arranged to be receivedwithin a corresponding recess formed in the pump body 10. In each case,the boss 42 and recess 44 together serve to resist movement of thefiller element 40.

An alternative location means is shown in FIG. 5. In this arrangement,locating pins 46 are fitted to the pump housing 22 or pump body 10,within the part forming the annular gallery 30, the pins 46 beingarranged to abut the ends of the filler element 40, and so resistmovement thereof.

It will be appreciated that these two forms of location means could beused in combination with one another, if desired.

Regardless as to the type of location means used, resisting movement ofthe filler element 40 ensures that the pump outlet 26 and outlet passage34 remain unobscured and in communication with one another.

It is thought that the invention may be applied to a number of knownpump designs, and may be retrofitted to existing pumps as well asincorporated into new pumps. Modifications to existing pump componentsto allow the incorporation of the invention are minimal.

Whilst specific embodiments of the invention are described herein, itwill be appreciated that a wide range of modifications and alterationsmay be made thereto without departing from the scope of the invention.

1-15. (canceled)
 16. A high pressure pump comprising: a pump body; apump housing within which at least part of the pump body is located; agallery defined between the pump body and the pump housing, the pumpbody having a pump outlet which communicates with the gallery, and thepump housing having an outlet port which communicates with the gallery;and a filler located within the gallery, the filler being located atleast in the part of the gallery most remote from the pump outlet. 17.The pump of claim 16, wherein the gallery is of annular form.
 18. Thepump of claim 17, wherein the filler extends about at least half of thecircumferential length of the gallery.
 19. The pump of claim 18, whereinthe filler extends about at least three quarters of the gallery.
 20. Thepump of claim 16, wherein a cross-sectional shape of the filler conformswith that of the gallery.
 21. The pump of claim 16, wherein the fillersubstantially fills at least part of the gallery furthest from the pumpoutlet.
 22. The pump of claim 16, wherein the filler is of anelastomeric material.
 23. The pump of claim 16, wherein the filler is ofmolded fluorocarbon form.
 24. The pump of claim 16, wherein the fillerforms an interference fit in the gallery.
 25. The pump of claim 16,further comprising locator means to resist movement of the filler withinthe gallery.
 26. The pump of claim 25, wherein the locator meanscomprises locator pins provided in the gallery and arranged to abut endsof the filler to resist movement of the filler.
 27. The pump of claim16, wherein the filler incorporates an integral projection configured tobe received within a corresponding recess formed in the pump body and/orpump housing to resist movement of the filler.
 28. The pump of claim 16,wherein adjacent the gallery, the pump body and pump housing are sealedto one another.
 29. The pump of claim 28, wherein adjacent the gallery,the pump body and pump housing are sealed to one another by o-ringseals.
 30. The pump of claim 16, further comprising at least one gerotorpump.